Abstract Oleuropein (OLE) is the major phenolic compound of olive leaves, known for its numerous health benefits. α-lactalbumin (ALA) is a milk protein constituting almost 20% of whey proteins with a high nutritional value owing to its essential amino acids. In this study, binding properties of OLE to ALA was explored by fourier transform infrared (FTIR) spectroscopy, fluorescent spectroscopy, dynamic light scattering, circular dichroism (CD) spectroscopy and molecular docking. The experimental results revealed a decrease in the fluorescence units due to binding process with fluorescent residues, especially with Trp104 which was then confirmed by CD spectroscopy and FTIR data and molecular docking. Also, the increase of OLE content resulted in the formation of a stable complex with a zeta potential near −15 mV. The size of the complex decreased after addition of more OLE to the protein which was attributed to the formation of hydrogen bonds and folding of protein structure. Moreover, molecular docking indicated that hydrogen bonding plays a crucial role in the formation of OLE-ALA complexes including amide groups of Asn44 and Asn56 with the hydroxy groups of OLE. These findings indicated that ALA may be an ideal nanocarrier to load OLE for further applications in food and pharmaceutical fields.

中文翻译：

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牛α-乳清蛋白与橄榄苦苷结合相互作用的实验和分子对接研究

摘要 橄榄苦苷 (OLE) 是橄榄叶的主要酚类化合物，以其众多的健康益处而闻名。α-乳清蛋白 (ALA) 是一种乳蛋白，占乳清蛋白的近 20%，由于其必需氨基酸，具有很高的营养价值。在这项研究中，通过傅里叶变换红外 (FTIR) 光谱、荧光光谱、动态光散射、圆二色 (CD) 光谱和分子对接研究了 OLE 与 ALA 的结合特性。实验结果表明，由于与荧光残基，尤其是与 Trp104 的结合过程，荧光单位减少，然后通过 CD 光谱和 FTIR 数据和分子对接证实。此外，OLE 含量的增加导致形成稳定的复合物，其 zeta 电位接近 -15 mV。向蛋白质中添加更多 OLE 后，复合物的大小减小，这归因于氢键的形成和蛋白质结构的折叠。此外，分子对接表明氢键在 OLE-ALA 复合物的形成中起着至关重要的作用，包括 Asn44 和 Asn56 的酰胺基团与 OLE 的羟基。这些发现表明，ALA 可能是一种理想的负载 OLE 的纳米载体，以进一步应用于食品和制药领域。